In many electronic systems, particularly those carried in vehicles such as aircraft where high-density packaging prevails because of space limitations, the efficient cooling of electronic components has become a significant problem. With the advent of large-scale integrated circuit (IC) modules containing many thousands of circuit elements, it has become possible to pack great numbers of electronic components together within a very small volume. As is well known, these integrated circuit modules generate significant amounts of heat during the course of their normal operation. Since most solid state devices are sensitive to excessive temperatures, a solution to the problem of the generation of heat by large scale IC's in close proximity to one another has become of increasing concern to industry.
A typical approach to cooling components in electronic systems in which devices containing integrated circuits are placed on circuit cards is to direct a stream of cooling air across the modules and/or cards. One of the principal disadvantages of this approach is that the air quality (moisture content, contamination, etc.) must be tightly controlled to inhibit corrosion, loss of cooling effectiveness, etc. This feature is necessary in the design of aircraft avionics in particular to assure system reliability. Cooling of components by this means necessitates a number of compromises to the overall system. These compromises include: high pressure drop; uniformity of component form factors; placing the components containing the integrated circuits further apart on the circuit cards; increasing the distance between circuit cards; and increasing the volume and velocity of cooling air directed over the components, which increase requires special considerations in the design of the housings containing the circuit cards and in the mechanical systems for delivering the cooling air.
Increases in the sophistication of electronic systems has brought about denser packaging of electronic components with attendant increases in power density and total card power. This has brought about the evolution of another technique which is a further conventional approach to cooling of card-mounted electronic components. This technique utilizes solid metal thermal mounting cards or plates which conduct the heat dissipated by electronic components to a heat sink disposed at the edge of each card. Such an approach, however, results in a large thermal resistance from the component mounting surface to the heat sink, which causes high component temperatures. In an effort to mitigate this problem with metal cards, the prior art has turned to heat pipe technology.
Heat pipes per se are, of course, well known, as are solid metal circuit cards or boards for mounting electronic components. In the prior art there are also teachings of metal circuit cards incorporating heat pipes for dissipating the heat generated by electronic components mounted on the cards.